CCS/TMS320F28069: CURRENT PROGRAMMED MODE USING RAMP GENERATOR AND COMPARATOR F28069 PICCOLO

Hi,

I am writing to let you know that a C2000 team member has been assigned to answer to this post.

Thanks
Vasudha

Daniel,

We will only be able to help you debug specific module failures. Have you identified the malfunction in your system that produces this behavior? If not, I would recommend that you break up your software into isolated tests to verify if the modules are working as expected.

For example, start with just the EPWM setup to make sure that the frequency is correct. Then add the Ramp Generator to monitor a static DC voltage on the comparator input. Verify that the EPWM trips as expected. You can confirm the decrement behavior by measuring the time between PWMSYNC and comparator trip at the DC level.

-Tommy

Hi Tommy thanks for your reply. I have tried using vissim software and psim software but still cant see a pwm signal using the ramp generator.

I just want to see a pwm signal just modifying the analog input using the ramp,. something like this picture.

I would appreciate if you have a code that let me do this.

Thank you

Daniel,

We won't be able to help you with VISSIM or PSIM here -- you will need to contact them directly for support.

For a C implementation, I recommend that you start with the epwm_dcevent_trip_comp example in C2000Ware and make sure that you can monitor the EPWM output and that it responds to your comparator trips.

Once that is working, you can port in your comparator settings to use the ramp generator to control the inverting input.

Starting from a known example will allow us to focus only on the few lines of code that are modified.

-Tommy

Hello Tommy thank you very much for your fast reply, i have been looking and testing that example but the result is not the desired, i want to configure the DAC at the midpoint value (512) ant the result i want to see is the same as an analog comparator(1 when input A2 is 3.3 and 0 when A2 is 0) but at the beggining i get a 470 Hz PWM signal and when i connect A2 to 0 V , GPIO00 goes high and does not do anymore, could you help me with this? i would appreciate so much

Thank you

(Example run like as follows):

//###########################################################################
// Description:
//! \addtogroup f2806x_example_list
//! <h1>ePWM DC Event Trip Comparator (epwm_dcevent_trip_comp)</h1>
//!
//! In this example ePWM1 is configured for PWM Digital Compare Event
//! Trip using Comparator1A and comparator1B pin inputs.
//! DCAEVT1, DCBEVT1 events are triggered by increasing the voltage on
//! COMP1B pin to be higher than that of COMP1A pin.
//! In this example:
//!    - ePWM1 has DCAEVT1 and DCBEVT1 as one shot trip sources
//!            DCAEVT1 will pull EPWM1A high
//!            DCBEVT1 will pull EPWM1B low
//!
//! Initially make the voltage level at COMP1A to be higher than that of COMP1B.
//! Increase voltage on inverting side of comparator(COMP1B pin) to trigger
//! a DCAEVT1, and DCBEVT1. ePWM1 will react to DCAEVT1 and DCBEVT1 as a 1 shot
//! trip. View the EPWM1A/B waveforms on an oscilloscope to see the effect of
//! the events.
//!
//! \b External \b Connections \n
//!  - EPWM1A is on GPIO0
//!  - EPWM1B is on GPIO1
//!  - COMP1A is on ADCA2
//!  - COMP1B is on ADCB2
//!  - pull COMP1B to a higher voltage level than COMP1A.
//
//###########################################################################
// $TI Release: F2806x C/C++ Header Files and Peripheral Examples V151 $
// $Release Date: February  2, 2016 $
// $Copyright: Copyright (C) 2011-2016 Texas Instruments Incorporated -
//             http://www.ti.com/ ALL RIGHTS RESERVED $
//###########################################################################

#include "DSP28x_Project.h"     // Device Headerfile and Examples Include File

// Prototype statements for functions found within this file.
void InitEPwm1Example(void);
__interrupt void epwm1_tzint_isr(void);

// Global variables used in this example
Uint32  EPwm1TZIntCount;
Uint32  EPwm2TZIntCount;

void main(void)
{
// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the F2806x_SysCtrl.c file.
   InitSysCtrl();

// Step 2. Initalize GPIO:
// This example function is found in the F2806x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
// InitGpio();  // Skipped for this example

// For this case just init GPIO pins for ePWM1, ePWM2, and TZ pins
   InitEPwm1Gpio();


// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
   DINT;

// Initialize the PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the F2806x_PieCtrl.c file.
   InitPieCtrl();

// Disable CPU interrupts and clear all CPU interrupt flags:
   IER = 0x0000;
   IFR = 0x0000;

// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example.  This is useful for debug purposes.
// The shell ISR routines are found in F2806x_DefaultIsr.c.
// This function is found in F2806x_PieVect.c.
   InitPieVectTable();

// Interrupts that are used in this example are re-mapped to
// ISR functions found within this file.
   EALLOW;  // This is needed to write to EALLOW protected registers
   PieVectTable.EPWM1_TZINT = &epwm1_tzint_isr;
   EDIS;    // This is needed to disable write to EALLOW protected registers

// Step 4. Initialize all the Device Peripherals:
// This function is found in F2806x_InitPeripherals.c
// InitPeripherals();  // Not required for this example

   
   EALLOW;
   SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1;                 // Enable Clock to the ADC
   AdcRegs.ADCCTL1.bit.ADCBGPWD = 1;                     // Comparator shares the internal BG reference of the ADC, must be powered even if ADC is unused
   DELAY_US(1000);                                         // Delay for Power Up
   SysCtrlRegs.PCLKCR3.bit.COMP1ENCLK = 1;               // Enable clock to the Comparator 1 block
   Comp1Regs.COMPCTL.bit.COMPDACEN = 1;                  // Power up Comparator 1 locally
   Comp1Regs.COMPCTL.bit.COMPSOURCE = 1;                 // Connect the inverting input to pin COMP1B
////////////////Uncomment following 2 lines to use DAC instead of pin COMP1B //////////////////////////////
   Comp1Regs.COMPCTL.bit.COMPSOURCE = 0;              // Connect the inverting input to the internal DAC
   Comp1Regs.DACCTL.bit.DACSOURCE=0;
   Comp1Regs.DACVAL.bit.DACVAL = 512;                    // Set DAC output to midpoint

///////////////////////////////////////////////////////////////////////////////////////////////////////////
   SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0;
   EDIS;

   InitEPwm1Example();

   EALLOW;
   SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1;
   EDIS;

// Step 5. User specific code, enable interrupts
// Initalize counters:
   EPwm1TZIntCount = 0;

// Enable CPU INT3 which is connected to EPWM1-3 INT:
   IER |= M_INT2;

// Enable EPWM INTn in the PIE: Group 2 interrupt 1-3
   PieCtrlRegs.PIEIER2.bit.INTx1 = 1;

// Enable global Interrupts and higher priority real-time debug events:
   EINT;   // Enable Global interrupt INTM
   ERTM;   // Enable Global realtime interrupt DBGM



// Step 6. IDLE loop. Just sit and loop forever (optional):
   for(;;)
   {
      __asm("          NOP");
   }

}

__interrupt void epwm1_tzint_isr(void)
{
   EPwm1TZIntCount++;

// Leave these flags set so we only take this
// interrupt once
//
// EALLOW;
// EPwm1Regs.TZCLR.bit.OST = 1;
// EPwm1Regs.TZCLR.bit.INT = 1;
// EDIS;

   // Acknowledge this interrupt to receive more interrupts from group 2
   PieCtrlRegs.PIEACK.all = PIEACK_GROUP2;

}




void InitEPwm1Example()
{

   EALLOW;
   EPwm1Regs.TBPRD = 6000;                         // Set timer period
   EPwm1Regs.TBPHS.half.TBPHS = 0x0000;            // Phase is 0
   EPwm1Regs.TBCTR = 0x0000;  
   

   // Setup TBCLK
   EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN; // Count up/down
   EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE;        // Disable phase loading
   EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV4;       // Clock ratio to SYSCLKOUT
   EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV4;

   EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;    // Load registers every ZERO
   EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;
   EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO;
   EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;

   // Setup compare
   EPwm1Regs.CMPA.half.CMPA = 3000;

   // Set actions
   EPwm1Regs.AQCTLA.bit.CAU = AQ_SET;             // Set PWM1A on CAU
   EPwm1Regs.AQCTLA.bit.CAD = AQ_CLEAR;              // Clear PWM1A on CAD


   EPwm1Regs.AQCTLB.bit.CAU = AQ_CLEAR;           // Clear PWM1B on CAU
   EPwm1Regs.AQCTLB.bit.CAD = AQ_SET;             // Set PWM1B on CAD
   
   // Define an event (DCAEVT1) based on TZ1 and TZ2
   EPwm1Regs.DCTRIPSEL.bit.DCAHCOMPSEL = DC_COMP1OUT;        // DCAH = Comparator 1 output
   EPwm1Regs.DCTRIPSEL.bit.DCALCOMPSEL = DC_TZ2;             // DCAL = TZ2
   EPwm1Regs.TZDCSEL.bit.DCAEVT1 = TZ_DCAH_LOW;              // DCAEVT1 =  DCAH low(will become active as Comparator output goes low)  
   EPwm1Regs.DCACTL.bit.EVT1SRCSEL = DC_EVT1;                // DCAEVT1 = DCAEVT1 (not filtered)
   EPwm1Regs.DCACTL.bit.EVT1FRCSYNCSEL = DC_EVT_ASYNC;       // Take async path
   
   // Define an event (DCBEVT1) based on TZ1 and TZ2
   EPwm1Regs.DCTRIPSEL.bit.DCBHCOMPSEL = DC_COMP1OUT;        // DCBH = Comparator 1 output
   EPwm1Regs.DCTRIPSEL.bit.DCBLCOMPSEL = DC_TZ2;             // DCAL = TZ2  
   EPwm1Regs.TZDCSEL.bit.DCBEVT1 = TZ_DCBH_LOW;              // DCBEVT1 =  (will become active as Comparator output goes low)    
   EPwm1Regs.DCBCTL.bit.EVT1SRCSEL = DC_EVT1;                // DCBEVT1 = DCBEVT1 (not filtered)
   EPwm1Regs.DCBCTL.bit.EVT1FRCSYNCSEL = DC_EVT_ASYNC;       // Take async path
         
   // Enable DCAEVT1 and DCBEVT1 are one shot trip sources
   // Note: DCxEVT1 events can be defined as one-shot.  
   //       DCxEVT2 events can be defined as cycle-by-cycle.
   EPwm1Regs.TZSEL.bit.DCAEVT1 = 1;
   EPwm1Regs.TZSEL.bit.DCBEVT1 = 1;

   // What do we want the DCAEVT1 and DCBEVT1 events to do?
   // DCAEVTx events can force EPWMxA
   // DCBEVTx events can force EPWMxB  
   EPwm1Regs.TZCTL.bit.TZA = TZ_FORCE_HI;           // EPWM1A will go high
   EPwm1Regs.TZCTL.bit.TZB = TZ_FORCE_LO;           // EPWM1B will go low

   // Enable TZ interrupt
   EPwm1Regs.TZEINT.bit.OST = 1;
   EDIS;
   
   
}

//===========================================================================
// No more.
//===========================================================================

Daniel,

It sounds like you are looking for the direct output of Comparator 1.  If you look at the GPIO MUX table in the TRM, you can configure the MUX for COMP1OUT on any of the GPIOs where the comparator output is available.  So if you change the GPIO1 mux setting from 0b01 (EPWM) to 0b11 (COMP1OUT), you should be able to see the comparator output directly on GPIO1 instead of EPWM1B.

The GPIO0 output is stuck high after trip because the EPWM1A is configured to react to the comparator with a One Shot Trip (OST) that is never cleared.  The code to clear the trip state is commented out in epwm1_tzint_isr().  When you implement the ramp generator, you will likely want a Cycle-By-Cycle (CBC) trip instead.

-Tommy

Hello tommy, thanks for your help. now i can use the comparator but cant with the ramp, i want to see my pwm signal but is too small with de rampdecvalue and i have used some values but still cant see for example a 0.99 duty cycle pwm signal. Here is my code, can you check it and tell me why i cant see a good pwm in gpio1? thanks:

#include "DSP28x_Project.h" // Device Headerfile and Examples Include File

void main(void)
{

InitSysCtrl();

DINT;

InitPieCtrl();

IER = 0x0000;
IFR = 0x0000;

InitPieVectTable();

EALLOW;

EPwm1Regs.TBPRD = 903; 

EPwm1Regs.CMPA.half.CMPA = 100; 
EPwm1Regs.TBPHS.half.TBPHS = 0; // Set Phase register to zero
EPwm1Regs.TBCTR = 0; // clear TB counter
EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP; // Asymmetrical mode
EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE; // Phase loading disabled
EPwm1Regs.TBCTL.bit.PRDLD = TB_SHADOW;
EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_SYNC_DISABLE;
EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1; // TBCLK = SYSCLK
EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;
EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;

EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO; // load on CTR = Zero
EPwm1Regs.AQCTLA.bit.ZRO = AQ_SET; // Set PWM1A on Zero
EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR;

SysCtrlRegs.PCLKCR0.bit.ADCENCLK = 1; // Enable Clock to the ADC

AdcRegs.ADCCTL1.bit.ADCBGPWD = 1; // Comparator shares the internal BG reference of the ADC, must be powered even if ADC is unused

DELAY_US(1000); // Delay for Power Up

SysCtrlRegs.PCLKCR3.bit.COMP1ENCLK = 1; // Enable clock to the Comparator 1 block

Comp1Regs.COMPCTL.bit.COMPDACEN = 1; // Power up Comparator 1 locally

//Comp1Regs.COMPCTL.bit.COMPSOURCE = 1; // Pin analogo B
Comp1Regs.COMPCTL.bit.COMPSOURCE = 0; //DAC interno

Comp1Regs.DACCTL.bit.DACSOURCE=1; //DAC INTERNO RAMPA

// Comp1Regs.DACCTL.bit.DACSOURCE=0; // DAC INTERNO CONSTANTE

//Comp1Regs.DACVAL.bit.DACVAL = 512; // Set DAC output to midpoint

Comp1Regs.DACCTL.bit.RAMPSOURCE=0; //Asigna PWMSYNC1

Comp1Regs.RAMPDECVAL_SHDW=10000; //Pendiente
Comp1Regs.RAMPMAXREF_SHDW=30000; //Maximo

GpioCtrlRegs.GPAMUX1.bit.GPIO1=11; //Gpio1 COMPOUT
GpioCtrlRegs.GPAMUX1.bit.GPIO0=1; //WATCH SYNC SIGNAL

EDIS;

for(;;)
{

}

}

Daniel,

You should double-check your MUX settings. It looks like you are writing decimal 11 and 01 instead of binary 0b11 and 0b01.

If you want a longer duty-cycle, you can reduce the DECVAL. With your current settings, you will trip in 3 cycles even with 0V applied to COMP1A.

-Tommy

Hello Tommy. I do not know exactly how the DECVAL works so i cant calculate the value i want to use. could you please tell me what DECVAL i have to use if i want a (3.3V)/(10us) slope in the ramp with a period of 10 us? (100 kHz)

Daniel,

The Ramp Generator is documented in the TRM.  It would probably be best for you to work out the details of how to configure it for your particular system because you will most likely need to optimize the settings after the first pass.  In a nutshell, the RAMPSTS register is initialized with RAMPMAXREF and is decremented by RAMPDECVAL on every clock  cycle until a RESET event is generated.

-Tommy

Yes Tommy, know i see what my error is. The RAMPSTS is RAMPMAXREF again when the DAC is equal to RAMPSTS. I want a signal which value is high before RAMPSTS is greater than DAC and LOW after RAMPSTS is lower than DAC (after the cmparation).

Cul you help me? i think is with a trigger

Daniel,

I'm not following your question. The DAC value is sourced directly from RAMPSTS.

-Tommy

Tommy the problem is that  RAMPSTS goes high when the reference is higher than the ramp and COMPSTS is just a pulse signal. I want a Pwm in low after the first time they cross. In short words. I want COMPSTS high when the ramp is higher and  COMPSTS low after they cross in time.

I have tried to do this for weeks but the ramp generator is crazy when it compares

Daniel,

The Ramp Generator was designed to follow a very specific state machine behavior (including the trip response) for PCMC applications and is not able to deviate much from it. I think you might be more successful by not using the Ramp Generator.

Would you be able to use the CPU or CLA to periodically update the DAC value to generate your own custom ramp and then use the COMPCTL[CMPINV] bit to invert the comparator output to meet your desired behavior?

-Tommy